Gestational Diabetes Mellitus Affects the Risk of Obstetric Anal Sphincter Injury: A Systematic Review and Meta-Analysis of Cohort Studies.

Introduction and hypothesis: High birth weight increases the risk of obstetric anal sphincter injury. Macrosomia is a well-known complication in pregnancies complicated by gestational diabetes mellitus. The aim of this study was to investigate whether gestational diabetes is a risk factor for obstetric anal sphincter injury. We hypothesized that women with gestational diabetes have an increased risk of obstetric anal sphincter injury.

Methods: We performed a systematic review and meta-analysis using the PubMed and Embase databases. Studies including numbers on women with and without gestational diabetes and with and without obstetric anal sphincter injury were included. Studies were assessed using the SIGN-methodology checklist to evaluate the quality and risk of bias. Extracted data was analyzed using RevMan 5.4 and the statistical software R.

Results: Twelve cohort studies were included for the meta-analyses. Overall, we found a slightly increased prevalence of obstetric anal sphincter injury among the women with gestational diabetes of 2.40% (95% CI; 2.37-2.43) compared to 2.31% (95% CI; 2.30-2.32) in women without diabetes. The meta-analysis revealed increased risk of obstetric anal sphincter injury in the gestational diabetes-group (RR 1.24 [95% CI; 1.12-1.37]) with a high level of heterogeneity (I² = 94%). Primiparous women with gestational diabetes had an increased risk of obstetric anal sphincter injury 6.65% (95% CI; 6.18-7.14) compared to 4.98% (95% CI; 4.89-5.08) in the control group, whereas the risk was not significantly increased in multiparous women.

Conclusions: The risk of obstetric anal sphincter injury is increased in primiparous women with gestational diabetes mellitus compared to women without gestational diabetes.